1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a device and a portable storage device which are capable of transferring a rights object (RO) which can guarantee a safe transfer of the RO between a device and a portable storage device.
2. Description of the Related Art
In recent years, research has been vigorously conducted on Digital Rights Management (DRM), which is a technology for protecting digital content that can be easily copied and distributed, and various services adopting DRM technology have been or are currently being commercialized. Digital data, unlike analog data, can be copied without causing any data loss, and it is easy to recycle, process, and distribute digital data compared to analog data. It is also possible to copy and distribute digital data at a low cost. However, the creation of digital content is costly, and time-consuming, and thus requires various techniques for protecting digital copyrights. Against this backdrop, the range of application of DRM has extended.
Related art techniques for protecting digital content generally focus on the prevention of illegitimate access to digital content. Therefore, only users who have paid fees for digital content are allowed to access the digital content, whereas users who have not paid any fees for the digital content are not allowed to access the digital content. However, if an authorized user who has paid fees for digital content and can thus legitimately access the digital content distributes the digital content to an unauthorized third person, the unauthorized third person may be able to consume the digital content without the need to pay any fees for the digital content, thereby causing a number of problems.
DRM basically allows unlimited access to digital content. However, DRM encrypts digital content and requires a predetermined license for the execution of such encrypted digital content, thereby assuring an effective protection of digital content.
FIG. 1 illustrates the concept of typical DRM. DRM mainly involves the protection of content using an encryption or scramble method and the management of a license necessary for accessing encrypted content.
FIG. 1 illustrates device A (10) and device B (50) which wish to access encrypted content, a content provider 20 which provides content, a rights object (RO) issuer (RI) 30 which issues an RO including a license necessary for executing content, and a certificate issuer 40 which issues a certificate.
Device A (10) may obtain encrypted content from the content provider 20. Thereafter, device A (10) may purchase an RO including a license necessary for the use of the encrypted content from the RI 30. Once the RO corresponding to the encrypted content is obtained, device A (10) may use the encrypted content.
Since the encrypted content can be freely distributed, device A (10) may freely transmit the encrypted content to device B (50). In order to reproduce the encrypted content, device B (50) also needs the RO corresponding to the encrypted content. Device B (50) may obtain the RO corresponding to the encrypted content from the RI 30.
The certificate issuer 40 issues a certificate including the name of an authorized device whose public key has been identified, a serial number of the certificate, the name of the certificate issuer 40, the public key of the authorized device, and a message indicating the expiration date of the certificate. A first device may determine whether a second device currently communicating with the first device is an authorized device based on a certificate, if any, issued to the second device by the certificate issuer 40.
However, no appropriate methods of transferring and copying an RO from a device to a portable storage device or vice versa and taking appropriate measures to deal with errors that may occur during the transfer and copy of an RO have been suggested.